Pons Anatomy PDF

PONS Dr. Ramadan El Gharbawy Professor of Anatomy & Embryology, Beirut Arab University, Lebanon Consultant of General Surgery, Egypt Ex-scholar at Emory, USA  OUTLINE AND OBJECTIVES Subtopics Objectives Revisit of the external features...

PONS Dr. Ramadan El Gharbawy Professor of Anatomy & Embryology, Beirut Arab University, Lebanon Consultant of General Surgery, Egypt Ex-scholar at Emory, USA  OUTLINE AND OBJECTIVES Subtopics Objectives Revisit of the external features of The student should be able to: pons 1. Recall the external features of Internal structure of pons: pons. 1. A transverse section of the pons 2. Describe the transverse section of at the level of the facial colliculus pons at these 2 levels. 2. A transverse section of the pons at the level of the principal sensory and motor nuclei of the trigeminal nerve  PONS- SITE AND EXTERNAL Midbrain FEATURES OF ANTERIOR SURFACE The pons is anterior to the cerebellum and Basilar sulcus connects the medulla oblongata to the Basis pontis midbrain. Trigeminal It is about 2.5 cm long. nerve The anterior surface is convex from side to Middle side and shows many transverse fibers that cerebellar converge on each side to form the middle peduncle cerebellar peduncle. Abducent A shallow groove in the midline, the basilar nerve groove, lodges the basilar artery. Vestibulocochlear On the anterolateral surface of the pons, nerve the trigeminal nerve emerges on each side. In the groove between the pons and the medulla oblongata, from medial to lateral, Facial nerve the abducens, facial, and vestibulocochlear nerves emerge. Medulla oblongata  PONS- POSTERIOR SURFACE The posterior surface of pons is triangular in shape and it forms the upper half of the floor Superior of the fourth ventricle. cerebellar Midbrain It is limited laterally by the superior cerebellar peduncle peduncles and is divided into symmetrical Median sulcus Medial Locus halves by a median sulcus. eminence coeruleus Lateral to the median sulcus is an elongated Facial elevation, the medial eminence, which is colliculus bounded laterally by a sulcus, the sulcus limitans (superior fovea). Middle crebellar The inferior end of the medial eminence is slightly expanded to form the facial colliculus. peduncle The floor of the superior part of the sulcus Area limitans is bluish-gray in color and is called the vestibuli substantia ferruginea (locus coeruleus). Lateral to the sulcus limitans is the area vestibuli produced by the underlying vestibular Sulcus limitans nuclei. Medulla oblongata  The basilar part of the pons contains small A TS OF THE PONS AT THE LEVEL OF THE FACIAL COLLICULUS pontine nuclei. The corticopontine fibers Descending tracts Pontine nuclei terminate on the cells of Corticospinal, Transverse fibers of pons these pontine nuclei corticonuclear, corticopontine and their axons- the transverse fibers of pons- cross the midline and intersect the corticospinal and corticonuclear tracts, breaking them up into small bundles. The transverse fibers of Middle pons enter the middle cerebellar cerebellar peduncle and peduncle are distributed to the cerebellar hemisphere. This connection forms the main pathway linking the cerebral cortex to the cerebellum. Fourth ventricle  The medial lemniscus is situated transversely in the most anterior part of the A TS OF THE PONS AT THE LEVEL OF THE FACIAL COLLICULUS tegmentum and is accompanied by the spinal Descending tracts Pontine nuclei Medial lemniscus and lateral lemnisci. Corticospinal, Transverse fibers of pons The facial nucleus lies corticonuclear, posterior to the lateral part corticopontine of the medial lemniscus. Abducent nerve The fibers of the facial nerve wind around the nucleus of the abducens nerve, producing the facial colliculus then pass anteriorly between the facial nucleus and the superior end of the nucleus Facial nerve of the spinal tract of the trigeminal nerve. Facial Middle The medial longitudinal nucleus cerebellar fasciculus- the main peduncle pathway connecting the vestibular and cochlear nuclei with the nuclei of oculomotor, trochlear, and abducens -is situated beneath the floor of the fourth ventricle on either side of the midline. Spinal nucleus and tract Abducent Geniculum of Fourth of trigeminal nerve nucleus facial nerve ventricle Medial longitudinal fasciculus  The medial vestibular nucleus A TS OF THE PONS AT THE LEVEL OF THE FACIAL COLLICULUS is situated lateral Descending tracts Pontine nuclei Medial lemniscus to the abducens Corticospinal, Transverse fibers of pons nucleus and is in corticonuclear, corticopontine close relationship Abducent nerve to the inferior cerebellar Vestibular peduncle. nerve The superior part of the lateral and Facial nerve the inferior part of the superior Facial Middle cerebellar vestibular nucleus nucleus peduncle are found at this Spinal nucleus level. and tract of The posterior and trigeminal nerve anterior cochlear nuclei are also Lateral and superior found at this level. Vestibulocochlear Abducent Geniculum of Fourth vestibular nuclei fibers nucleus facial nerve ventricle Medial longitudinal fasciculus  The spinal nucleus of the A TS OF THE PONS AT THE LEVEL OF THE FACIAL COLLICULUS trigeminal nerve Pontine nuclei Medial lemniscus and its tract lie Descending tracts Corticospinal, Transverse fibers of pons on the corticonuclear, anteromedial corticopontine aspect of the Trapezoid body Abducent nerve inferior Trapezoid nucleus cerebellar Central tegmental Vestibular nerve peduncle. tract The trapezoid Facial nerve body- made up of fibers derived from the Facial nucleus Middle cerebellar cochlear nuclei peduncle and the nuclei of Spinal nucleus the trapezoid and tract of body- runs trigeminal transversely in nerve Inferior the anterior part cerebellar ped. of the Lateral and superior tegmentum. Vestibulocochlear fibers Abducent Geniculum of facial nerve Fourth ventricle vestibular nuclei nucleus Medial longitudinal fasciculus  A TS OF THE PONS AT THE LEVEL OF THE PRINCIPAL SENSORY AND MOTOR NUCLEI OF THE TRIGEMINAL NERVE The basilar part Transverse pontine fibers Trapezoid body Medial lemniscus shows the same internal features Descending fibers of cortical origin Trapezoid nucleus shown at the facial colliculus level. Lateral lemniscus The trapezoid Meddle body and the cerebellar medial lemniscus peduncle are situated in the same position as they were at the level of facial colliculus. The lateral and spinal lemnisci lie at the lateral extremity of the medial lemniscus.  A TS OF THE PONS AT THE LEVEL OF THE PRINCIPAL SENSORY AND MOTOR NUCLEI OF THE TRIGEMINAL NERVE The motor Transverse pontine fibers Trapezoid body Medial lemniscus nucleus of the Descending fibers trigeminal nerve is of cortical origin Trapezoid nucleus situated beneath Lateral lemniscus the lateral part of the fourth Meddle ventricle within cerebellar peduncle Trigeminal nerve the reticular formation. The emerging motor Motor nucleus of trigeminal nerve fibers travel anteriorly through the substance of the pons and exit on its anterior surface. Fourth ventricle  The principal A TS OF THE PONS AT THE LEVEL OF THE PRINCIPAL sensory nucleus of the trigeminal nerve SENSORY AND MOTOR NUCLEI OF THE TRIGEMINAL NERVE is situated on the lateral side of the Transverse pontine fibers Trapezoid body motor nucleus; it is Descending fibers Medial lemniscus continuous inferiorly of cortical origin with the nucleus of Trapezoid nucleus the spinal tract. The entering sensory Lateral lemniscus fibers travel through Superior olivary nucleus the substance of the Meddle pons and lie lateral cerebellar to the motor fibers. Trigeminal nerve peduncle Central The superior tegmental cerebellar peduncle tract is situated Motor nucleus of Medial posterolateral to the trigeminal nerve longitudinal motor nucleus of fasiculus the trigeminal nerve. It is joined by the anterior Principal sensory nucleus spinocerebellar of trigeminal nerve Mesencephalic tract tract. of trigeminal nerve Superior cerebellar peduncle Cerebellar folium Superior medullary velum Fourth ventricle THANK YOU